I've long wanted to improve the pistons and valve gear on my locomotives. Cale Leiphart's piston design is awesome, but the way I've been using it it's a bit plain by itself. Carl's recent masterpiece inspired me to go the extra step.

While it uses the same basic design as Carl's, because my pistons are oriented perfectly vertical, and Carl has more room to work with because he isn't using thin liftarms as connecting rods, the L-Bar looks very strange on my locomotive. It's too far down the length of the locomotive, and far too high above the drivers. The real valve gear, at least on this locomotive, should be centered on the axles.

So I decided to spend some more time with the design, to see if I couldn't get it to sit lower and more closely mimic the motion of the valve gear. Here's what I came up with:

I'm much happier with this design. It isn't perfect, but I think it does the job very admirably. Eventually I'd like to add valve gear like this to all of my TSRR steam roster, and maybe to a few others as well.

And just for the sake of being complete, here's a nice video of the real #500:

Thank you everyone, I appreciate it. This was a lot of fun, more fun building than I've had in quite some time. It didn't feel like work. Now I need to order parts, I only had enough for this one side of the locomotive!

I have to be careful, though, about adding such valve gear will-nilly to my MOCs. I was watching some video last night and came to the realization that Texas State Railroad #201 lacks almost any form of external valve gear, it predates it. Whoops!

This is good Tony, especially for a mechanism with no modded parts. It gets closer to the amount of valve gear that OO models have. They tend to cheat and have a moving expansion link but static parts between there and the cylinders.

I did the full Walschaert's valve gear for my BR Class 9F but had to mod a few parts. I did something similar for my LMS Garratt, thoguh that has to widen it so that the train motors can swivel inside the driving wheels. this meant I also had to raise the expansion links to clear the platforms! Some of the modded parts I could argue TLG should be making anyway, such as the 1x2 "+o" thin liftarm and 1x3 "ooo" thin liftarm. I have asked them for a 40mm pulley like the 24mm one before.

The way I developed since then does it with fewer mods to liftarms to make the valve gear rods and cranks (no cut up 24mm pulleys!), but with modded model team wheels as an improvement from 40-tooth cogs ('cos TLG don't make train wheels big enough, even as blind drivers):
Carl told me about the cut up baseplate technique. 1 baseplate can make quite a few 1x4s for liftarms!

It shows the possibility of doing all 3 cylinders of a Gresley Pacific (such as Flying Scotsman) or maybe a 2-6-2 V2 like Green Arrow. I hope it will form the basis for my future large steam engine sometime.